gravimetric analysis

What is another name for gravimetric analysis

Gravimetry

What is gravimetric analysis

The quantitative isolation of a substance by precipitation and weighing of the precipitate

What is an analyte

The substance to be analyzed.

What is a precipitating reagent?

The reactant used to precipitate the analyte

What must the precipitate in gravimetric analysis be like

It must be a pure substance of definite chemical composition

What is one advantage of gravimetric analysis over volumetric analysis

Impurities are more likely to be noticed, allowing for correction

What is one disadvantage of gravimetric analysis

It is generally more time-consuming

What are two uses of gravimetric analysis

(i) To determine the percentage of sulfate in lawn fertilizer.
(ii) To determine the concentration of chloride in water.

Why must a high-purity solvent (like deionized water) be used to dissolve the sample?

To prevent contamination from ions in the solvent, which could cause co-precipitation and alter the final mass.

Why is the solution heated (digested) and the precipitant added slowly with stirring?

To promote the formation of large, filterable crystals and to minimize the formation of fine, impure precipitates that are difficult to work with.

What does it indicate when adding more precipitant no longer forms a precipitate?

 It is the visual endpoint, indicating that the precipitation reaction is complete and the analyte ions are fully consumed.

Why is the original container rinsed, and why are small volumes of cold wash liquid used?

Rinsing ensures quantitative transfer of all precipitate. Small, cold volumes remove soluble impurities while minimizing the solubility loss of the precipitate.

What is a major risk when using vacuum filtration (like a Büchner funnel), and how can it be mitigated?

The suction can tear the filter or create channels, allowing fine precipitate particles to be lost. Mitigation: use a sintered-glass crucible.

What is the significance of achieving a constant mass for the precipitate in the drying oven?

It proves the precipitate is completely dry and of constant composition, ensuring an accurate final mass measurement.

Why must the crucible containing the precipitate be cooled to room temperature in a desiccator before weighing?

To prevent weighing errors caused by air currents (convection) and buoyancy effects from hot air, and to prevent moisture absorption during cooling.